It is known in the art that headless pivot rods may be used in flexible modular belts, preferably made of plastic modules connected together by the pivot rods. Such headless pivot rods however in normal belt usage and loading, generally under tension, must be retained to prevent axial movement out of position to interfere with optimal belt performance. Some solutions to this problem are disclosed in U.S. Pat. No. 4,858,753 to W. G. Hodlewsky, Aug. 22, 1989.
Thus, spring plugs are suggested, for example, forced into outer apertures alongside the belt edge. However, these plugs interfere with a smooth belt edge desirable to prevent wear when engaging sidewalls and the like. Also they represent added cost in forming extra belt parts which also require labor cost in assembly.
Alternative suggestions to leave the end apertures open without such plugs, require oblong inner belt journalling apertures different from end apertures. This adds construction costs and problems and is not always acceptable when it is desired to eliminate play in the modular interconnection joint at the pivot rod. Also it does not positively prevent headless pivot rods from entering end apertures and interfering with belt performance. Furthermore, particularly with narrow belts, the alternative use of the pivot rod journalling aperture in the end links eliminates the desirable positive journalled linkage coupling between modules of the critical end plate that may be in contact with side rails, for example.
In a copending application of the common assignee of this application U.S. Ser. No. 07/586,389 to J. M. Lapeyre for "Apparatus to Allow Non-destructive Removal of Pivot Rods in Modular Plastic Conveyor Belts" there is disclosed a pivot rod stopping member integrally molded as a tabular flexible extension on a plastic modular section belt edge member having enough resiliency to be forcibly moved out of its position blocking the journalling pivot pin apertures so that pivot pins cannot be entered or exited without bending the tabular extension out of the way. While this feature has considerable merit, it also removed the possibility of structural changes in the critical belt edge portion of the module including the option of a substantially continuous belt edge surface. Also the range of resilience of a tabular extension on firmly affixed module end structure limited the flexibility and accordingly the number of repetitive work cycles of life, the range of plastic materials, which might under some conditions be required to be stiff or "case hardened" for meeting other design criteria of a plastic belt, and imposed conditions that made it difficult to remove or enter pivot rods without considerable force or special tools.
Accordingly it is an object of this present invention to improve the state of the art by removing the aforesaid deficiencies, and to provide a self contained plastic modular belt assembly with fewer parts which positively retains pivot rods in their axial working position during normal use of the belt, but which facilitates ready "toolless" manual operation for belt assembly and pivot rod removal.